[PATCH v2 1/8] event: signal when livetree has been built

[Neil Armstrong]

On 11/04/2025 14:47, Caleb Connolly wrote:
> OF_LIVE offers a variety of benefits, one of them being that the live
> tree can be modified without caring about the underlying FDT. This is
> particularly valuable for working around U-Boot limitations like lacking
> USB superspeed support on Qualcomm platforms, no runtime OTG, or
> peripherals like the sdcard being broken (and displaying potentially
> worrying error messages).
> 
> Add an event to signal when the live tree has been built so that we can
> apply fixups to it directly before devices are bound.
> 
> Signed-off-by: Caleb Connolly <caleb.connolly at linaro.org>
> ---
>   common/event.c  |  3 +++
>   include/event.h | 18 ++++++++++++++++++
>   lib/of_live.c   | 11 +++++++++++
>   3 files changed, 32 insertions(+)
> 
> diff --git a/common/event.c b/common/event.c
> index dda569d447851f559a83f98fb7b1f3543156eab5..8d7513eb10b61919e1e784481dfdcc076be14986 100644
> --- a/common/event.c
> +++ b/common/event.c
> @@ -47,8 +47,11 @@ const char *const type_name[] = {
>   	"ft_fixup",
>   
>   	/* main loop events */
>   	"main_loop",
> +
> +	/* livetree has been built */
> +	"of_live_init",

"of_live_built" ?

>   };
>   
>   _Static_assert(ARRAY_SIZE(type_name) == EVT_COUNT, "event type_name size");
>   #endif
> diff --git a/include/event.h b/include/event.h
> index 75141a192a48b0931667632f41be8ff4d6139f7c..1d267f1d10547642d381fa287ab4981a2bf03543 100644
> --- a/include/event.h
> +++ b/include/event.h
> @@ -152,8 +152,17 @@ enum event_t {
>   	 * A non-zero return value causes the boot to fail.
>   	 */
>   	EVT_MAIN_LOOP,
>   
> +	/**
> +	 * @EVT_OF_LIVE_BUILT:
> +	 * This event is triggered immediately after the live device tree has been
> +	 * built. This allows for machine specific fixups to be done to the live tree
> +	 * (like disabling known-unsupported devices) before it is used. This
> +	 * event is only available if OF_LIVE is enabled and is only used after relocation.
> +	 */
> +	EVT_OF_LIVE_BUILT,
> +
>   	/**
>   	 * @EVT_COUNT:
>   	 * This constants holds the maximum event number + 1 and is used when
>   	 * looping over all event classes.
> @@ -202,8 +211,17 @@ union event_data {
>   	struct event_ft_fixup {
>   		oftree tree;
>   		struct bootm_headers *images;
>   	} ft_fixup;
> +
> +	/**
> +	 * struct event_of_live_built - livetree has been built
> +	 *
> +	 * @root: The root node of the live device tree
> +	 */
> +	struct event_of_live_built {
> +		struct device_node *root;
> +	} of_live_built;
>   };
>   
>   /**
>    * struct event - an event that can be sent and received
> diff --git a/lib/of_live.c b/lib/of_live.c
> index 90b9459ede313e492e28c8556c730f3bd8aaa9df..c1620616513c2e32448b4a6d156a9162d97c76b7 100644
> --- a/lib/of_live.c
> +++ b/lib/of_live.c
> @@ -10,8 +10,9 @@
>   
>   #define LOG_CATEGORY	LOGC_DT
>   
>   #include <abuf.h>
> +#include <event.h>
>   #include <log.h>
>   #include <linux/libfdt.h>
>   #include <of_live.h>
>   #include <malloc.h>
> @@ -320,8 +321,9 @@ int unflatten_device_tree(const void *blob, struct device_node **mynodes)
>   
>   int of_live_build(const void *fdt_blob, struct device_node **rootp)
>   {
>   	int ret;
> +	union event_data evt;
>   
>   	debug("%s: start\n", __func__);
>   	ret = unflatten_device_tree(fdt_blob, rootp);
>   	if (ret) {
> @@ -334,8 +336,17 @@ int of_live_build(const void *fdt_blob, struct device_node **rootp)
>   		return ret;
>   	}
>   	debug("%s: stop\n", __func__);
>   
> +	if (CONFIG_IS_ENABLED(EVENT)) {
> +		evt.of_live_built.root = *rootp;
> +		ret = event_notify(EVT_OF_LIVE_BUILT, &evt, sizeof(evt));
> +		if (ret) {
> +			log_debug("Failed to notify livetree build event: err=%d\n", ret);
> +			return ret;
> +		}
> +	}
> +
>   	return ret;
>   }
>   
>   void of_live_free(struct device_node *root)
>